A baby's first stool is called meconium. It is a mixture of the secretions from the alimentary glands together with lanugo, pigment and cells from the wall of your baby’s bowel.
After a day or two, a breastfed baby will have soft yellow stools. During the first few weeks she will probably pass stools after every feed. Don’t worry about constipation – it is highly unlikely in breastfed babies. Some breastfed babies may not pass a stool for four to five days.